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Yoshiki Sasai
Sasai, c. 2012
Born	5 March 1962 Hyogo, Japan
Died	5 August 2014(2014-08-05) (aged 52) Kobe, Hyogo, Japan
Cause of death	Suicide by hanging
Nationality	Japanese
Alma mater	Kyoto University
Awards	Osaka Science Prize Inoue Prize for Science
Scientific career
Fields	Biology
Institutions	RIKEN
Doctoral advisor	Shigetada Nakanishi
Website	www.cdb.riken.jp/sasai/ (archived)

Yoshiki Sasai (笹井 芳樹, Sasai Yoshiki, 5 March 1962 – 5 August 2014) was a Japanese stem cell biologist. He developed methods to guide human embryonic stem cells (hESCs) into forming brain cortex, eyes (optic cups), and other organs in tissue culture. Sasai worked at the Riken Center for Developmental Biology (CDB) in Kobe, and was Director of the Laboratory for Organogenesis and Neurogenesis. Following his involvement in the 2014 STAP cell controversy, Sasai was found dead at Riken from an apparent suicide.

Yoshiki Sasai was born in 1962 in Hyogo, Japan. He received his medical degree from Kyoto University's School of Medicine in 1986. In 1993 Sasai was awarded a PhD from the Kyoto University School of Medicine, and served a residency at Kobe Municipal General Hospital.

Sasai worked as a research fellow at Edward M. De Robertis's laboratory at UCLA School of Medicine until 1996. ^[1] Sasai became an associate professor at Kyoto University in 1996, and a full professor in 1998. In 2003 he moved to the RIKEN Center for Developmental Biology as Director of the organogenesis and neurogenesis group. ^[2]

Sasai was known for developing methods to grow stem cells into organ-like structures. ^{[3] [4] [5] [6] [7] [8] [9] [10] [11]} In 2012, Sasai became the first stem cell researcher to grow an optic cup from human cells. ^[12]

In 2014 Sasai was a co-author on two papers published in Nature, shortly thereafter retracted, that described stimulus-triggered acquisition of pluripotency or "STAP" cells. ^{[13] [14] [15]}

A subsequent investigation by Riken found that Sasai's co-author, Haruko Obokata, had committed scientific misconduct in the STAP cell experiments, and criticized Sasai for inadequate supervision of Obokata. ^{[16] [17] [18]} In response to the Riken investigation, Sasai described himself as "overwhelmed with shame", ^[19] and following a month of hospitalization was found dead from an apparent suicide by hanging on August 5, 2014. ^{[20] [21] [22] [23]}

2010 Osaka Science Prize for his work on in vitro recapitulation of brain development

2012 Inoue Prize for Science. ^[2]

2013 Hans Sigrist Prize ^[24]

• List of scientific misconduct incidents